1. Field of the Invention
The present invention relates to an interlocking apparatus and, more particularly, to an interlocking apparatus having multiple elements to ensure reliability.
2. Description of the Related Art
FIG. 3 is a view for explaining the function of a conventional interlocking apparatus. FIG. 3 shows a robot hand portion 1, robot arms 2 and 3, a robot mounting portion 4, three motors 5, a robot moving rail 6, system front covers 7 and 9, door switches 8 and 10, a controller 11 of the robot, a driver 12, a relay 13, and a conventional interlocking apparatus 14. The robot mounting portion 4 can move in the X direction. The motors 5 extend, contract, and rotate the robot arms 2 and 3 and drive the robot mounting portion 4 in the X direction. The door switches 8 and 10 respectively detect that the system front covers 7 and 9 are opened/closed. The driver 12 drives the motors 5 in the robot. The relay 13 connects or disconnects the driver 12 and motors 5 to or from each other. The interlocking apparatus 14 turns off the relay 13 under predetermined conditions. An OR circuit 15 receives outputs from the door switches 8 and 10. A latch circuit 16 (RS flip-flop) is set when an output from the OR circuit 15 becomes active. The OR circuit 15 and latch circuit 16 constitute the interlocking circuit 14. A release switch 17 resets the latch circuit 16.
In this configuration, when the system front cover 7 or 9 is opened, this state is detected by the door switch 8 or 10. The latch circuit 16 in the interlocking circuit 14 is set accordingly to turn off the relay 13. When the relay 13 is OFF, the drive operations of all the motors 5 in the robot are stopped to ensure safety.
In this prior art, the safety is ensured. However, while the system front cover 7 or 9 is open, even if the robot does not exist near the open system front cover 7 or 9, or even if the operator does not access the interior of the system, the whole system is stopped by the interlocking apparatus 14. Considering convenience for maintenance, this prior art is not optimum.
In various types of industrial systems of recent years, the interlocking function is performed on the basis of the determination of various conditions. For example, in the above case, not only the door switches are provided respectively to the front covers 7 and 9 of each system, but also robot detection sensors for detecting the presence/absence of the robot are provided near the front covers 7 and 9, respectively, of each system, and insertion detection sensors for detecting an insertion by means of an optical sheet beam are provided to the opening portions of the front covers 7 and 8, respectively, of each system. The drive operation of the robot is stopped only when the system front cover 7 or 9 is open, the robot exists near the opening portion of the system front cover 7 or 9, and some insertion exists in this opening portion.
In recent years, safety requirements that are stricter than before have been imposed on various types of industrial systems. In particular, regarding an interlocking apparatus, the following requirements have begun to arise. More specifically, 1 the interlocking apparatus must be formed by using highly reliable electromechanical components such as a relay and a switch; 2 when using semiconductor components such as ICs or transistors, they must be used in a duplex manner; and 3 no software must be used.
It is practically difficult to achieve the various types of detection functions and determinations on conditions described above with only electromechanical components in accordance with the above item 1. Inevitably, the semiconductor components are used in a duplex manner in accordance with the above item 2.
It is, therefore, significant to ensure the reliability of the duplex portion of the interlocking apparatus.